Alkylation process



Patented May 4, 1948 UNITED STATE OFFICE Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing.

Original application October 9.,

1943, Serial No. 505,661. Dividedand this application May 23, 1945, Serial-No. 595,491

Claims. (0!. 260-68324) This invention relates to the alkylation of parafiinic hydrocarbons with olefinic hydrocarbons, and is more particularly concerned with the catalytic alkylation of isoparafiinic hydrocarbons with olefinic hydrocarbons in the presence of hydrofluoric acid. 7

It iswell known in the art to eiiect the union of parafiinic hydrocarbons and olefinic hydrocarbons by processes broadly called alkylation processes. In alkylation processes, a charge including a mixture of paraflinic hydrocarbon called the parafiinic reactant, and an olefinic hydrocarbon called the olefinic reactant, is introduced into a reaction zone under suitable reaction conditions of temperature and pressure, referred to as alkylating conditions, to yield a product called the hydrocarbon alkylate, which comprises -constituents of a saturated character. Since the alkylating conditions cause also polymerization of the olefinic reactant, it is necessary to maintain a relatively low concentration of the olefinic reactant in the charge. Generally speaking, the more severe the alkylating conditions, i. e. the higher the temperatures and pressures, the higher the yield of hydrocarbon alkylate. lE he only limit to the pressure used appears to be the feasibility of-maintaining high pressures. On the other hand, the temperature used is limited by the degradation of the hydrocarbon reactants in the charge to low molecular weight hydrocarbons, and the occurrence of secondary reactions, including polymerization .of the olefinic reactant, under high temperature conditions, that substantially reduce the purity of the product obtained.

Alkylationmay be conductedat high temperatures and pressures, on the order of over 900 F. and over 4000 pounds per square inch, respectively; or may be carried .out at lower temperatures and -pressures,- in the presence of substances that facilitate the union of parafiinic hydrocarbons and olefinic hydrocarbons, hence called alkylation catalysts, thereby assuring a high yield of desired hydrocarbon alkylateby' avoiding extensive degradation of the reactants, the occur,- rence of secondary reactions, and appreciable polymerization of the olefinic reactants. The two methods are known as thermal alkylation and as catalytic alkylation,respectively.

Severalmethods are known jor the catalytic alkylation of Paraiiinic hydrocarbons with olefinic hydrocarbons. Thus, it is known to carry out th a ky aic of e afiin h d oca bons with olefinic hy carbons i the Pre ence f a kyl-ation catalysts consisting essentiallyoi metal and 2 non-metal halides, such as aluminum chloride, boron trifiuoride and the like, of sulfuric acid, of phosphoric-acid, or metal phosphates, of acti-' vated clays, and the like. In these processesthe alkylation catalysts are used in amounts varying between about 10% and 200% by weight, on the charge, depending .upon the alkylation catalyst and conditions used. However, it would seem that these and similar ,alkylation catalysts have one or more definite disadvantages, among which the-most important are romotion 9f the aforementioned secondary reactions and loss vof alkylation catalytic activity on the part of the catalyst, relatively rapidly. Nptably, the metal halides form additional compounds with olefinic reactants, that u mately de e eratev into tarry masses that represent loss of catalytic activity .of the alkylation catalysts andloss of potential olefinic reactant. similarly, s'ulfuricacid causes the formation .of various organic compounds that ultimately reduce the catalytic activity .of the acid necessitating periodic removal of the sulfuric acid contaminated with these compounds, and replacement with fresh acid. It must be noted further, that sulfuric acid is. a powerful oxidizing-agent and its use, .at temperatures above about .F., entails extensive undesirable secondary reactions that consume the acid and the valuable hydrocarbon reactants.

Concentrated hydrofluoric acid, when used as an alkylation catalyst, apparently does not have these disadvantages. It is a non-oxidizing and nonreducing substance and hence, it may be used atelevated temperatures without any ofthe undesirable results referred to hereinbefore. :Several processes are known in the art for catalytic ally alkylating parafiinic hydrocarbons with olefinic hydrocarbons in the presence ,of hydrofluoric acid. Generally. speaking, the processis carried out with the hydrocarbon reactants substantially in liquid phase .and in the presence .of sufficient amountsof hydrofluoric acid to effect substantial saturation of the hydrocarbon liquid with hydrogen-fluoride.

In some instances, thealkylation catalyst consists of two or more of the alkylation catalysts re.- ferred to. Thus, it is known to effect the alkylation of paraffinic hydrocarbons with olefinic hydrocarbons in the presence of alkylation catalysts consisting of mixtures of sulfuric acid and hydrofluoric acid, or of mixtures of sulturic acid and hydrochloric or ,hydrobromic acids, or of mixtures of .a metal halideand the corresponding hydrogen halide.

, It is also known that certain ubsta c s cal d promoters, promote the catalytic action of alkylation catalysts, particularly those consisting essentially of metal halides. Accordingly, several processes have been proposed wherein small amounts of these promoters, on the order of about 0.5 to 3% by weight, on the charge, are added to the alkylation catalysts to promote their alkylation catalytic activity.

I have now found that the alkylation catalytic activity of anhydrous hydrogen fluoride may be appreciably enhanced through the addition of organic or inorganic halogen compounds, excluding fluorides, or of elementalhalogens, excluding fluorine.

It is an object of the present inventionwto provide an eflicient process for catalytically alkylating parafiinic hydrocarbons with olefinic hydrocarbons. Another object of the present invention is to provide an efficient process for catalytically alkylating parafiinic hydrocarbons with olefinic hydrocarbons in the presence of hydro fluoric acid. A more specific object is to provide a process for catalytically alkylating paraflinic hydrocarbons with oleflnic hydrocarbons to produce high yields of high-octane blending agents for the manufacture of improved motor fuels. A

very important object of the present invention is to afford a process capable of carrying out the above objects by carrying out the reaction in the presence of halogens, other than fluorine, or of halogen compounds, other than fluorides. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

Broadly stated, the present invention provides a process for alkylating paraffinic hydrocarbons with oleflm'c hydrocarbons, which comprises contactinga paraflinic hydrocarbon and an oleflnic hydrocarbon in a reaction zone under alkylating conditions, with an alkylation catalyst consisting essentially of anhydrous hydrogen fluoride, in the presence of organic or inorganic halogen compounds, excluding fluorides, or of elemental halogens, excluding. fluorine.

While it is well known that hydrofluoric acid is a good alkylation catalyst, see U. S. Patent No. 2,267,730, my invention indicates very definitely that halogen compounds, other than fluorides and elemental halogens, other than fluorine, improve the quality and quantity of the hydrocarbon alkylate, when these compounds or elemental halogens are added to the hydrogen fluoride, before the alkylation operation is carried out.

When a mixture of a parafiinic hydrocarbon,

particularly a low-boiling isoparaiiinic hydrocarbon such as isobutane, anhydrous or concentrated hydrofluoric acid, and an olefinic hydrocarbon such as isobutylene, is maintained at a reaction temperature, a union takes place between the paraflinic hydrocarbon and the olefinic hydrocarbon to produce a higher boiling paraflinic hydrocarbon which generally represents structurally, the addition of the original hydrocarbon reactants. Valuable high-octane blending agents for the manufacture of improved motor fuels may be thus produced. For example,

g cm I H ira HF ([JH; H on, CHz-CH C=G-CHa OHrC-CCCH; 333 Ill 4 CHziH vIsobutane lsobutylene Isooctane In carrying out the alkylation of paraiiinic hydrocarbons with olefinic hydrocarbons in the presence of hydrofluoric acid as alkylation cata lyst, the hydrofluoric acid should be used in amounts of at least about 10% and up to about 60% of the total charge, on a liquid volume basis. Aqueous solutions of hydrofluoric acid in which hydrogen fluoride is present in concentrations greater than may be used, but the use of to hydrofluoric acid is to be preferred, and substantially anhydrous hydrofluoric acid or hydrogen fluoride is very efiective as an alkylation catalyst in the process of my invention.

The reaction temperature may be varied over a wide range depending upon the parafiinic reactant used in the reaction. Generally speaking the temperature of reaction Varies between about 0 F. and about 400 F., lower temperatures being used when the more reactive parafiinic or olefinic reactants are employed and higher temperatures becoming necessary when the less reactive paraflinic OI'rOlEfiHi-C reactants are employed. For instance, when the paraffinic reactant is isobutane or isopentane, and when the olefinic reactant is propylene or butylene, alkylation may be readily eifected at temperatures varying between about 35 F. and about 100 F.

Ordinarily, alkylation in the presence of hydrofluoric acid as the alkylation catalyst, is carried out under super atmospheric pressure, and pressures varying between about 20 pounds per square inch and 500 pounds per square inch have been found ample in most instances. As a general rule, the most suitable pressure is more or less dependent upon the particular temperature involved and when high temperatures are employed, pressures as high as 2000 pounds per square inch may be employed, if desired.

In carrying out alkylation of parafiinic hydrocarbons with olefinic hydrocarbons, it is well known, as stated hereinbefore, to maintain a relatively low concentration of the olefinic reactant in the reaction zone, in order to preclude extensive polymerization of the oleflnic hydrocarbon. Accordingly, it is advisable to maintain the olefinic hydrocarbon concentration in the reaction zone below about 25% by volume, and preferably, between about 7% and about 12% by volume. In continuous operation, this is effected by introducing the olefinic reactant over a period of time corresponding to the reaction period.

The reaction period during which the olefinic reactant is introduced into the reaction zone to react with the paraiflnic reactant to produce the hydrocarbon alkylate, depends upon the temperature, and to a certain extent, upon the pressure. Ordinarily, a reaction period varying between 15 minutes and 2 hours is satisfactory. At higher temperatures, the timeof reaction may be as low as 5 minutes and even lower, while at lower temperatures, the'time of reaction'may be as high as 5 hours.

It must be understood, that the reaction variables are more or less interdependent, hence when one is arbitrarily fixed, the limits within which the'others may be varied, are somewhat restricted. In any particular instance, the most desirable conditions can be readily ascertained by one skilled in the art, the preferred ranges of these variables having been indicated hereinbefore.

The parafiinic and olefinic hydrocarbons to be used in my process may be derived from any suit able source, as is well known in the art, and may be used either inthe pure state or'in admixture with other constituents not undesirable. The paraffinic and olefinic hydrocarbons usually employed in the preferred operation of manufacturing motor fuels will be the normally gaseous parafiinic hydrocarbons, except methane and ethane, and the normally gaseous olefinic hydrocarbons, propylene, butylene and. pentene, as is well understood in the art. A conventional and preferred source of paraflinic and oleflnic hydrocarbons is the fixed gases obtained around petroleum refineries. These fixed gasesmay furnish substantially all the desired paraflinic and olefinic hydrocarbons, or it may be necessary'or desirable to obtain additional supplies, as is well understood. Additional oleflnic hydrocarbons, if required, may be formed from a portion of the parafiinic hydrocarbons. On the other hand, additional amounts of parafli'nic hydrocarbons may be admixed in order to increase the concentration of paraifinic hydrocarbons to a desired magnitude.

The organic and inorganic halide'a'other than fluorides, and the element-a1 halogens, other than fluorine, that are used in accordancewith the process of my invention, may be solids, liquids or gases under normal conditions. It is suspected that the improved results-obtained with these substances, is probably due more to an ultimate activation of the olefinic reactant during the alkylation operation, than to promoter action on the hydrogen fluoride catalyst, although the latter should not be excluded altogether. Whatever the function of these substances is, the quality and quantity of the hydrocarbon alklyate are substantially improved through their use. In view of the relative uncertainty of the manner in which these substances function during the alkylation operation, these substances may be referred to more correctly, as hydrogen fluoride additives, rather than as promoters or as activators.

The hydrogen fluoride additives of my invention include various metallic chlorides, bromides and iodides, for example, anhydrous calcium chloride; organic halogen compounds, excepting fluorides, such as alkyl chlorides, bromides and iodies, especially secondary and tertiary halides; aralkyl halogen compounds, excepting fluorides; aliphatic and, aromatic acid chlorides, bromides and iodides; non-metallic halides, excepting fluorides, such as phosphorus and sulfur chlorides, bromides and iodide; hydrogen halides, excepting of course hydrofluoric acid; and finally, the halogens themselves, excepting fluorine.

I especially prefer to use, as hydrogen fluoride additives, alkyl chlorides and bromides, particularly tertiary alkyl chlorides and bromides and secondary alkyl chlorides and bromides, hydrogen halides other than hydrofluoric acid, and halogens other than fluorine. Specific and preferred hydrogen fluoride additives that may be mentioned by way of non-limiting examples are: tertiary butyl chloride, tertiary butyl bromide, tertiary amyl chloride, tertiary amyl bromide, isopropyl chloride, isopropyl bromide, proylene chloride, propylene bromide, hydrogen chloride, hydrogen bromide, chlorine and bromine.

The amounts of hydrogen fluoride additives ordinarily used in my process, vary between about 5% and about 50% with respect to the amount of hydrogen fluoride employed. Larger amounts appear to be unnecessary; however, it must be noted that they may be employed if desired, although no additional advantages result therefrom. The amounts of hydrogen fluoride additives used may be smaller, on the order of 1% to about 5%, when larger amounts of hydrogen fluoride catalyst are employed.

- bons in the presence'of hydrogen fluoride, but

the following examples are 'sufliciently characteristic:' N

311111 .Run2 Run3 Run4' Isobntane, weight in grams 261' 270 265 275 lsobutylenaweight in grams- '87 87' 87 I 87 Hydrogen fluoride, weight in grams 35 35 35 Hydrogen fluoride additive, l

- weight in grams None 1 3 2 l0 3 18 Temperature, O 25-30 25-30 25-30 25-30 Pressure in pounds pcrv square inch.' 4080 40-80 4080 .40- Hydrocarbon alkylate, weight in grams 152 176 196 201 Total octancs 90 G.l25 0. Wt.

in grams 91 102 112. 5 118.5 Isooctane 98 C.10l 0,, weight in grams 39 47 54 69 I ncl. 'r-but i tidiide. 'lrbutyl-bromide.

- The octane fraction of the hydrocarbonalkylate produced-by my process contains 2,2,4-trimethyl pentane in predominant amounts, and the results of infra-red analysis indicate the presence also of 2,3,3 trimethy1pentane. This octane is not present in the hydrocarbon alkylates obtained when the alkylation is conducted in the absence of my hydrogen fluoride additives and under the conditions outlined hereinbefore. Infra-red analyses also indicate that the hydrocarbon alkylates obtained when alkylation is carried out in the absence of the hydrogen fluoride additives of my invention and under conditions outlined in the preceding table, contain appreciable concentrations of unsaturates which are not present in the hydrocarbon alkylates obtained in the process of my invention.

The present application is a division of copending application Serial Number 505,661, filed October 9, 1943.

The present invention may be embodied in other, specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

I claim:

1. In a process for alkylating a paraffinic hydrocarbon having at least three carbon atoms with an olefinic hydrocarbon having at least three carbon atoms, which includes contacting said paraffinic hydrocarbon with said oleflnic hydrocarbon in a reaction zone under alkylating conditions. in the presence of a hydrogen fluoride alkylation catalyst, and maintaining said paraffinic hydrocarbon in excess over said olefinic hydrocarbon in said reaction zone so that alkylation is the principal reaction; the improvement which comprises contacting said parafiinic hydrocarbon and said olefihic hydrocarbon with a hydrogen fluoride alkylation catalyst in said reaction zone, in thepresence of added amounts of a material selected from the group consisting of hydrogen chloride, hydrogen bromide and hydrogen iodide.

2. The process of manufacturing high-octane gasoline, which comprises contacting a normally gaseous isoparaffinic hydrocarbon and a normally gaseous olefinic hydrocarbon having at least three carbon atoms in a reaction zone under Numerous experimental data could be ada: flumi alkxi'sttamia m at; added amounteefii amom'dei, d: maintaining said: nelmelw m ydr narhm in. exemqvezs midgase m e m-1c! hsent. mention zoneso that aims 1a, is; the e imimt reaettma 3. The processof manufacturing high-octane asnlina. which. comprises. eontactin a. no m l gasenus isonaztamnie hydrocarbon and a normanyaseaus olefini' hydrocarbon v ng at leastfihxee carbon atoms in a reaction zone unden alkylating cnnditiens, with a. hmirmenflmfide alkylation catalyst; in the presence of added amounts of hydrogen bromide and; mamtaining said normallx gaseens: isoparefinic hxdmcarben in excess over saizi normaliiw Eamon-a olefinie h?- d'rocarborr in said; reaction zone se that alt-syn.- tinn ia the prtncipaneactiom 4. The process at manufacturing highenqtane gasoline, which comprisea=- eentacting". isehutane and isnbutylene, m a reaetion zone under alkylating'conditions, with a.- hydrogen fluoride a-lkyiationcatalyst, in the presence of added" amounts of ydtmm and maintaining said; isubutune in excess aver sat in. saint. re-

eti m na. s that allmlattm is he reeetiem;

5, Thegpmeess 0L manuiactmzing; higmaetane gasglinea, Whisk: cQmpt-ises eontaetlng isabutane amt i sobutglene; m a. reactien zoneunder' alkylatins, eond-i-tlensh with: aflmam fluoride alkylaatm eezitalyat,v 1n. the pzzesence of added amqunts or bnom1de and: maintaining. said; 180- butane in excessouer said ispbutylene in: said reaction zone, sq that alkylatmnt is the grineipal neaetiom,

JAQQB B. MEADOW.

FERENCES. CHEER foliewmgi refienences are,- ofi record in the file this patent:

' STATES PATENTS 

